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THE  NORMAN  W.  HENLEY  PUBLISHING  Co. 

132  NASSAU  STREET.  NEW  YORK 


PRACTICAL  SILO 
CONSTRUCTION 


A    TREATISE 


ILLUSTRATING  AND  EXPLAINING  THE  MOST  SIMPLE  AND  EASIEST 
PRACTICAL  METHODS  OF  CONSTRUCTING  CONCRETE  SILOS  OF 
ALL  TYPES;  WITH  UNPATENTED  FORMS  AND  MOLDS.  THE 
DATA,  INFORMATION  AND  WORKING  DRAWINGS  GIVEN  IN  THIS 
BOOK  WILL  ENABLE  THE  CONCRETE  BUILDER  TO  SUCCESSFULLY 
CONSTRUCT  ANY  OF  THE  MOST  PRACTICAL  TYPES  OF  CONCRETE 
SILOS  IN  USE  TODAY. 

By 
A.    A.    H^OUGHTON 

Author  of  "Concrete  from  Sand  Molds,"  "Ornamental  Concrete 
Without  Molds,"  Etc.,  Etc. 


TWENTY  ILLUSTRATIONS 


NEW  YORK 

THE  NORMAN  W.  HENLEY  PUBLISHING  CO. 

132  NASSAU  STREET 

1911 


COPYRIGHTED,  1911, 

BY 
THE  NORMAN  W.  HENLEY  PUBLISHING  Co. 


FOREWORD 

IT  is  the  purpose  of  the  writer  to  present  in  this 
series  of  books  a  complete  explanation  of  various 
successful  methods  of  concrete  construction  that  may 
be  employed  by  the  beginner  as  well  as  by  the  more 
experienced  worker.  I  shall  endeavor  to  give  the 
details  of  molds  and  ideas  that  are  not  covered  by 
patents,  such  as  may  be  easily  and  cheaply  con- 
structed; hence  the  reader  is  not  compelled  to  pur- 
chase expensive  patented  molds  before  putting  into 
practise  the  many  successful  types  of  concrete  con- 
struction I  have  exhaustively  described  in  this  series. 
There  is  no  practical  value  to  the  reader  in  explain- 
ing a  patented  system  of  construction,  other  than  a 
few  words  on  its  merits,  as  the  owners  of  same  are 
always  pleased  to  give  this  information;  hence  in 
going  outside  the  beaten  track  of  concrete  authors 
and  presenting  ideas,  systems,  and  molds  that  are 
practical,  successful  in  operation,  and,  above  all, 
easily  and  simply  constructed,  I  trust  that  I  have 
merited  the  sincere  gratitude  of  all  fellow  workers 
in  the  concrete  field  who  seek  such  information. 
Yours  very  truly, 

A.  A.  HOUGHTON. 

215500 


PREFACE 

THE  concrete  silo  has  easily  demonstrated  its 
superiority  over  all  other  types  of  silo  construction, 
and  to-day  stands,  in  the  opinion  of  every  practical 
builder,  as  the  nearest  to  perfection  of  any  type  of 
structure  for  the  preservation  of  green  crops  in  si- 
lage. When  we  hark  back  to  the  civilization  of  the 
past  centuries,  we  find  that  the  silo  is  but  another 
modern  adaptation  of  ancient  building  construction, 
bringing  more  forcibly  to  our  notice  "that  there  is 
nothing  new  under  the  sun." 

In  this  treatise  I  have  endeavored  to  show  the 
requirements  of  silo  construction  to  insure  success, 
and  the  best  methods  of  complying  with  these  requi- 
sites when  concrete  is  the  material  for  the  struc- 
ture. The  importance  of  the  foundation  is  fully 
treated,  as  the  structure  can  be  no  stronger  than  the 
foundation  upon  which  it  rests,  and  it  is  far  better 
to  err  on  the  safe  side  in  construction  of  the  founda- 
tion than  to  find  it  inadequate  for  the  load  it  must 
carry.  As  the  solid  wall  silo  is  the  usual  type  erected 
at  the  present  time  in  monolithic  construction,  I 
have  presented  one  of  the  most  practical  and  posi- 
tively the  most  simple  and  easily  constructed  wood 
form  that  has  been  published  up  to  the  present  time. 

9 


10  PREFACE 

The  fact  that  this  wood-clamp  silo  form  is  rigid  and 
amply  strong  for  the  work  of  a  construction  that 
requires  the  minimum  of  lumber,  and  is  easily  raised 
in  a  manner  that  makes  it  almost  impossible  to  get 
the  walls  from  a  perfect  vertical  line,  should  be  of 
vast  interest  to  every  contractor  or  silo  builder. 

The  molding  of  monolithic  silo  walls,  with  a 
continuous  air-chamber  between  same,  is  also  fully 
treated;  one  by  employing  a  simple  and  easily  con- 
structed automatic  wall-clamp,  and  also  by  the  well- 
known  method  of  building  the  walls  from  blocks  or 
units. 

The  construction  of  silos  from  concrete  plaster  or 
stucco  is  also  explained,  as  well  as  the  reinforcement 
of  silos,  with  tables  for  the  proper  placing  of  this 
reinforcing  material.  The  different  types  of  silo 
doors,  and  two  methods  of  making  a  concrete  roof — 
plain  and  ornamental — for  the  silo,  are  explained  in 
detail. 

Believing  that  this  volume  will  fill  every  need  of 
the  contractor  for  practical  and  easily  understood 
instruction  upon  this  subject,  and  that  it  will  be  of 
value  to  you,  I  am, 

Very  truly  yours, 

A.  A.  HOUGHTON. 
February,  1911, 


TABLE  OF  CONTENTS 

PAGE 

THE  CONCRETE  SILO 13 

REQUIREMENTS  OF  A  SILO 14 

SIZE  OF  SILO  TO  ERECT 17 

FOUNDATIONS  FOR  THE  SILO .  20 

FOUNDATION  WITH  FLOOR  BELOW  GROUND-LEVEL        .      .  23 

FORMS  FOR  MONOLITHIC  WALLS  WITHOUT  AIR-CHAMBER   .  23 

A  SIMPLE  AND  INEXPENSIVE  SILO  FORM 25 

METHOD  OF  RAISING  FORMS .  32 

USING  AUTOMATIC  CLAMP 35 

PLASTERED  SILOS 38 

CONCRETE  BLOCK  SILOS 41 

CONCRETE  FOR  SILO  WORK         .      .      .      .      .      .      .      .49 

REINFORCEMENT  OF  SILOS 50 

DOORS  FOR  THE  SILO      .            55 

SILO  ROOFS 60 

ORNAMENTAL  ROOF  OR  WALL  FOR  SILO  62 


PRACTICAL 
SILO  CONSTEUCTION 

THE  concrete  silo  has  within  the  past  year  demon- 
strated to  the  majority  of  builders  its  superiority 
over  all  other  types  of  silo  construction.  Not  only 
for  the  great  durability  of  properly  made  concrete 
does  it  base  its  claims  for  consideration,  but  in  the 
fact  that  it  can  be  made  water-proof  and  frost-proof, 
as  well  as  being  absolutely  air-tight,  has  done  much 
to  advance  the  concrete  silo  in  the  favorable  opinion 
of  the  farmer  as  well  as  the  builder.  In  the  process 
of  ensilage  we  are  only  adapting  to  our  present  day 
needs  a  method  of  preserving  grains  and  green  crops 
that  has  been  in  successful  use  for  centuries.  The 
fact  that  the  masonry  silos  or  granaries  of  the  an- 
cient Egyptians  were  built  on  practically  the  same 
plan  as  our  present-day  silos,  and  that  this  method 
of  ensilage  was  in  successful  use  for  centuries,  will 
be  of  interest  to  the  doubter  who  believes  that  stone, 
either  natural  or  artificial,  is  not  the  best  material 
for  the  construction  of  a  structure  for  the  preser- 
vation of  grain  or  any  crop.  In  fact,  the  greatest 
enemy  of  the  concrete  silo  to-day  is  the  man  who 

13 


14  PRACTICAL  SILO  CONSTRUCTION 

has  a  silo  to  sell  of  some  other  material.  The  unani- 
mous verdict  of  those  who  have  built  of  concrete  is 
that  it  has  given  the  greatest  satisfaction,  with 
practically  no  future  expense  for  painting  and  re- 
pairs, which  is  a  large  item  with  the  wood  and  metal 
silo.  Adding  to  this  the  fact  that  a  properly  con- 
structed concrete  silo  is  everlasting,  we  have  a  bal- 
ance in  favor  of  concrete  that  no  other  building 
material  can  hope  to  overcome. 

The  word  silo  is  used  to  designate  a  closed  pit  or 
reservoir,  in  which  green  fodder  or  dry  grain  may 
be  placed  for  preservation.  Ensilage  is  the  process 
of  preserving  the  grain  or  green  fodder  in  the  pit  or 
silo.  Silage  is  the  preserved  fodder  or  grain,  or 
the  results  produced  by  the  process  of  ensilage.  In 
present-day  use  the  silo  is  employed  for  green  crops 
almost  exclusively,  and  upon  our  dairy  farms  of  this 
country  green  corn  is  usually  the  material  for  our 
silage;  in  other  countries,  clover  and  other  grasses, 
tares,  rye,  and  oats,  are  used  to  produce  silage. 

REQUIREMENTS   OF  A   SILO 

The  requisites  of  a  successful  silo  are,  first,  its 
air-tight  features.  This  can  be  accomplished  for  the 
first  year  or  so  in  the  lighter  and  less  durable  meth- 
ods of  construction ;  but,  after  the  first  few  years  of 
use,  the  seams  or  joints  of  the  wood  silo  will  spread 
apart  and  thus  admit  air.  This  demands  repairs; 
and,  in  the  years  of  use,  it  is  easily  to  be  seen  that 
the  slight  extra  cost  of  a  concrete  silo  is  saved  many 


PRACTICAL  SILO  CONSTRUCTION  15 

times  over  in  the  upkeep  or  repairs  necessary  to  the 
wood  or  metal  silo. 

These  arguments,  which  are  understood  by  those 
who  have  had  the  experience,  apply  also  to  the  other 
features  of  a  successful  silo— durability,  and  a  small 
repair  bill. 

The  silo  is  best  when  water-proof  and  frost-proof. 
The  penetration  of  moisture  through  the  silo  is  very 
apt  to  injure  the  silage,  as  the  preservation  of  the 
moisture  is  necessary  to  the  process,  while  the  freez- 
ing of  the  silage  is  very  annoying  when  feeding  it 
out,  as  large  masses  of  it  will  adhere,  by  freezing, 
to  the  wall  of  the  silo,  and  cannot  be  removed  until 
thawed  out.  This  does  not  injure  the  silage,  but  is 
an  annoyance  when  feeding  the  silage,  in  the  winter 
months. 

The  water-proofing  of  the  silo  can  be  easily  ac- 
complished by  using  any  of  the  water-proofing  com- 
pounds on  the  market,  or  by  making  the  concrete  in 
the  walls  as  dense  as  possible.  By  using  a  wet  mix- 
ture of  concrete,  the  mortar  will  the  more  tightly 
pack  together,  thus  reducing  the  size  of  the  pores 
for  the  admittance  of  moisture  to  the  silage,  as  well 
as  preventing  the  moisture  in  the  green  fodder  from 
escaping  through  the  walls.  Again,  by  the  use  of 
a  brush,  coat  over  the  completed  walls,  of  ordinary 
Portland  cement,  one  part;  hydrated  lime,  one-half 
part;  this  is  mixed  with  water  to  the  consistency  of 
paint  and  applied  with  a  wide  brush  to  the  walls  as 
soon  as  forms  are  removed,  and  aids  materially  in 


16  PRACTICAL  SILO  CONSTRUCTION 

water-proofing  the  silo.  In  ordinary  practise  two  or 
three  thin  coats  of  this  material  applied  over  the 
walls  will  be  ample  water-proofing  for  the  purpose, 
as  this  brush  coat  fills  the  pores  of  the  concrete  in 
an  effective  manner.  Caution  must  be  observed 
in  using  this  brush  coat,  that  it  is  not  applied  too 
thick,  as  then  it  will  craze  or  check,  thus  supplying 
cracks  for  the  admission  of  moisture.  By  having  it 
quite  thin,  and  brushing  well  when  spreading,  the 
purpose  is  accomplished  with  two  coats,  successfully 
filling  the  pores  but  not  applying  more  material  than 
will  perfectly  bond  with  the  concrete  in  the  wall. 

The  thickness  of  wall  does  not  prevent  the  free- 
zing of  the  silage,  for  concrete,  as  with  stone  ma- 
sonry, is  not  frost-proof  in  any  ordinary  thickness 
as  employed  for  walls.  The  most  successful  method 
to  avoid  freezing  of  the  silage  is  to  build  double 
walls  to  the  silo,  with  an  air-chamber  between  same. 
This  is  accomplished  in  the  block  construction  and 
also  in  the  monolithic  type  of  construction.  While 
freezing  is  not  an  injury  to  the  silage,  the  protection 
of  a  double  wall  against  same  is  a  positive  preventa- 
tive  against  this  annoyance  in  feeding — a  feature 
that  is  of  value  in  our  cold  winters  of  the  Northern 
States. 

The  double  wall  silo  with  sealed  air-chambers  is 
also  an  assurance  against  the  danger  of  air  reaching 
the  silage,  as  well  as  moisture  penetrating  the  walls. 


PRACTICAL  SILO  CONSTRUCTION  17 

SIZE    OF    SILO   TO   ERECT 

The  diameter  of  the  silo  should  not  be  larger  than 
will  enable  the  silage  to  be  fed  from  the  entire  top 
each  day.  If  the  top  is  not  fed  out  every  twenty- 
four  hours  the  silage  is  apt  to  mold;  so,  in  construc- 
tion, the  number  of  animals  to  be  fed  from  same 
should  be  the  greatest  consideration  in  planning  the 
size. 

A  cubic  foot  of  silage  will  vary  in  weight  from  35 
to  50  pounds.  In  estimating,  40  pounds  to  the  cubic 
foot  may  be  taken  as  the  weight,  with  safety,  in 
approximately  determining  the  storage  capacity  of 
the  silo. 

The  amount  fed  to  a  cow  each  day  varies  from  40 
to  60  pounds,  when  used  with  other  feed ;  hence,  by 
employing  a  safe  average  of  50  pounds  daily  for  each 
animal,  it  is  possible  to  estimate  the  best  size  of  silo 
to  erect  for  the  purpose,  as  each  animal  at  this  rate 
would  consume  three-quarters  of  a  ton  in  each  thirty 
days.  It  is  always  better  to  err  slightly  on  over- 
capacity than  otherwise,  as  the  settling  of  the  silage 
that  takes  place  after  filling  will  vary  with  the  con- 
dition of  the  fodder  at  the  time  of  filling;  so  this  can- 
not be  positively  estimated.  This  is,  of  course,  only 
in  reference  to  the  height  of  the  silo,  as  the  layer 
that  is  to  be  removed  each  day  in  feeding,  to  prevent 
molding  of  the  ensilage,  can  be  accurately  deter- 
mined so  as  to  consume  a  layer  of  two  or  three 
inches  in  depth  daily. 


18 


PRACTICAL  SILO  CONSTRUCTION 


The  following  table  will  enable  the  size  of  the 
silo  to  be  quite  accurately  estimated  as  to  height 
when  the  diameter  has  been  determined.  Thus,  by 
multiplying  the  capacity  per  foot  of  height  by  the 
proposed  height  of  silo,  you  easily  secure  the  ap- 
proximate capacity  in  tons. 


TABLE   I 

SIZE  OF  SILOS 

diameter  contains     f   ton  to  each  foot  of  height. 


1 

1  J    to 
3 
4 

Q  S 

ns  to  each  foot  of  height. 

.     ..     , 

t    t 

<     «      t 

,     . 

6' 

8' 
10' 
12' 
U' 
15' 
16' 
18' 
20 ' 
25' 


The  usual  practise  is  not  to  make  the  inside  di- 
ameter of  the  silo  greater  than  one-half  the  height, 
consequently  a  diameter  of  more  than  20'  inside 
is  not  often  required;  where  larger  quantities  are 
needed  the  best  practise  is  to  build  several  silos  of 
smaller  diameter  and  capacity,  thus  exposing  as  little 
of  the  silage  to  the  air  between  feeds  as  possible. 

By  the  table  given  it  will  be  seen  that,  to  furnish 
the  silage  ration  for  a  herd  of  10  cows — the  lowest 
number  that  it  is  practical  to  build  a  silo  for — they 
will  consume  about  one-fourth  of  a  ton  daily,  or  45 
tons  in  180  days,  60  tons  in  240  days.  This  would 
require  a  silo  10 '  in  diameter  and  33 '  in  height  for 
6  months'  feeding,  allowing  3'  for  the  settling  of 


PRACTICAL  SILO  CONSTRUCTION  19 

the  silage,  which  cannot  be  accurately  estimated,  as 
heretofore  explained.  In  a  silo  12'  in  diameter  the 
height  for  6  months'  feeding  would  be  23',  with 
the  same  allowance  for  settling.  For  8  months' 
feeding  the  height  of  a  12'  silo  would  be  30',  on  the 
above  basis.  As  the  10 '  diameter  would  permit  the 
feeding  of  500  pounds  daily  to  remove  a  2"  layer 
of  silage,  while  the  12'  diameter  would  remove  ap- 
proximately about  |",  it  will  be  seen  that  the  10' 
diameter  would  be  the  most  practical  from  an  eco- 
nomical point  of  view. 

LOCATION   OP   SILO 

The  location  of  the  silo  should  be  such  that  it 
permits  easy  feeding,  and  when  possible  to  place 
upon  the  south  of  the  barns  there  is  always  less 
annoyance  in  removing  the  silage  in  bad  weather, 
when  it  is  constructed  separate  from  the  barn ;  also 
the  animals  may  then  be  often  fed  in  racks  in  the 
yard  with  less  labor  in  placing  the  silage  before  them. 

Where  the  floor  of  silo  is  placed  too  far  below 
ground-level  it  is  found  to  be  more  annoyance  in  re- 
moving the  last  few  feet  of  silage;  hence  the  floor- 
level  should  not  be  more  than  4 '  below  ground-level 
to  insure  an  easy  removal  of  the  contents.  The  mat- 
ter of  drainage  is  not  needful  to  consider,  as  the 
material  placed  in  the  silo  has  a  large  percentage  of 
water,  which  the  silo  must  retain  to  prevent  the 
silage  from  "dry  firing";  so  the  foundation  should 
be  made  as  water-proof  as  possible,  which  will 


20 


PRACTICAL  SILO  CONSTRUCTION 


also  keep  out  the  surface  water  as  well  as  retain 
the  moisture  in  the  silage, 

FOUNDATIONS    FOR   THE    SILO 

These  must  be  given  careful  attention,  as  the  life 
of  the  structure  depends  upon  same.  The  practise 
of  constructing  the  foundation  in  a  haphazard  man- 
ner is  to  be  regretted;  for,  when  we  consider  the 
weight  of  the  concrete  structure,  as  well  as  the  weight 
of  the  column  of  silage  it  contains,  the  vast  impor- 
tance of  amply  protecting  this  in  constructing  an 
adequate  foundation  is  easily  to  be  seen. 

At  Fig.  1  is  shown  the  usual  type  of  foundation 
for  a  concrete  silo,  where  the  floor  of  same  is  at 
ground-level,  as  indicated  at  a.  The  dotted  lines 
at  6  show  the  form  of  constructing  footings,  which 
are  determined  by  the  size  of  silo. 

The  following  table  will  aid  in  determining  the 
diameter  and  size  of  the  footing  courses  for  the 
different  sizes  of  silos  usually  constructed. 

TABLE   II 

DIAMETER  AND  SIZE  OF  FOOTING  COURSES 


Diameter  of  Silo 
in  Feet. 

For  Stone,  Clay,  or  Gravel. 

For  Sand  or  Loam  Soil. 

A. 

B. 

C. 

D. 

A. 

B. 

C. 

D. 

10  '  . 

to  to  co  «o  co  co  co 

<N  *•#  CO  t>  CO  O  <N 
rH  r-t  i—  1  r-t  r-i  <N  CM 

j  to  to  to  to  to  to  to 

1 
1 
1 
1 
1 
1 
1 

12  " 
12" 
IS" 
IS" 
U" 

16" 

CO  CO  CO  CO  CO  CO  CO 
CO  1C  t-  00  Oi  i-l  CO 

r-1  rH  r-l  »-l  i—  1  C<i  C\J 

V  V  V  V  ^  V  V 

CO  CO  CO  CO  CO  CO  CO 

00  CO  00  00  00  CO  CO 

12  " 
12" 
13" 
13" 
14  " 
15* 
16" 

12'  

14'  
15  '  

16  ' 

18' 

20  '  .   ... 

FIG.  1. —Foundation  for  a  silo  with  floor  at  ground-level. 


22  PRACTICAL  SILO  CONSTRUCTION 

In  the  preceding  table,  A  refers  to  the  outside 
diameter  of  the  foundation,  including  footing;  B  to 
the  width  of  the  footing  or  bearing  course  on  the 
soil;  C  to  the  thickness  of  the  footing  course,  and 
D  to  the  thickness  of  the  wall  of  foundation  that 
rests  upon  footing  course,  and  extends  to  ground- 
level. 

The  foundation  course  should  be  placed  of  con- 
crete that  is  not  leaner  than  1:2:4  of  well-graded 
sand  and  gravel  or  crushed  stone.  This  is  well 
tamped,  and  allowed  to  harden  permanently  before 
the  walls  of  silo  are  erected  upon  same,  otherwise 
the  weight  of  the  concrete  placed  [upon  the  foun- 
dation may  develop  defects  in  the  foundation  that 
would  not  happen  if  it  had  ample  time  and  oppor- 
tunity to  thoroughly  cure  before  the  walls  were  con- 
structed above  ground-level. 

Where  the  soil  is  firm  the  excavation  can  be  em- 
ployed to  furnish  the  mold  for  the  outside  walls  of 
foundation,  by  cutting  it  down  to  the  size  desired; 
the  forms  for  the  inside  wall  surface  can  then  be 
erected  and  the  concrete  placed. 

Where  the  forms  will  permit,  the  floor  of  silo  can 
be  laid  at  the  time  the  foundation  is  placed,  and  thus 
form  a  part  of  same ;  but,  where  the  wall  forms  de- 
mand supporting  uprights  inside  the  silo,  the  floor 
must  then  be  placed  after  the  silo  walls  are  com- 
pleted. 


PRACTICAL  SILO  CONSTRUCTION  23 

FOUNDATION   WITH   FLOOR   BELOW   GROUND- 
LEVEL 

At  Fig.  2  is  shown  the  usual  type  of  silo  founda- 
tion, where  the  floor-level  is  below  the  ground-level, 
which  is  designated  by  a  a  in  illustration.  The 
footing  course  is  shown  by  the  dotted  lines  6  6,  and 
at  all  times  forms  a  part  of  the  foundation-wall  to 
ground-level.  The  best  practise  is  to  also  make  the 
footing-course  a  part  of  the  floor  of  silo,  although  it 
cannot  be  done  when  uprights  must  be  erected  in- 
side the  forms,  as  previously  explained;  in  which 
case  the  footing  extends  the  proper  distance  outside 
and  inside  the  foundation-wall,  as  shown  by  dotted 
lines,  and  the  floor  is  laid  inside  this  when  the  silo 
walls  are  complete.  Where  the  silo  floor  is  not  laid 
with  the  foundation,  extreme  care  must  be  employed 
to  make  the  joint  between  edge  of  floor  and  footing 
water-tight,  otherwise  surface  water  will  collect  in 
the  bottom  of  silo. 

The  thickness  of  foundation-walls,  given  in  Ta- 
ble II,  apply  to  the  foundations  where  the  floor  is  at 
ground-level  as  well  as  to  those  below  ground-level. 

FORMS   FOR   MONOLITHIC   WALLS   WITHOUT 
AIR-CHAMEER 

After  the  foundation-walls  have  had  ample  time 
to  permanently  harden — so  that  they  will  bear  the 
weight  of  the  concrete  for  walls  of  silo — the  forms 
for  the  type  of  wall  you  desire  to  erect  are  placed, 
with  the  necessary  staging  or  uprights  to  carry  the 


FIG.  2,— Foundation  for  a  silo  with  floor  below  ground-level. 


PRACTICAL  SILO  CONSTRUCTION  25 

wall  forms  to  the  height  of  the  silo.  These  uprights 
should  be  placed  plumb,  and  securely  braced  or  held 
by  guy  wires  or  ropes,  so  that  they  will  serve  as  a 
guide  in  building  the  silo  walls  absolutely  vertical. 

A   SIMPLE    AND    INEXPENSIVE    SILO    FORM 

The  most  simple  silo  form  or  centering,  and  one 
that  requires  the  least  amount  of  lumber  to  erect,  is 
shown  in  detail  in  Fig.  3.  The  wood  clamp  is  built 
of  2x4"  strips  that  are  at  least  12"  longer  than  the 
sheet  steel  used  for  centering  is  wide.  Thus,  if  the 
sheet  steel  is  the  usual  size  of  24x101",  the  sides 
of  the  clamp  will  be  3 '  in  length.  The  upper  cross- 
piece  to  clamp  is  cut  long  enough  to  lap  onto  the 
side-pieces  and  leave  space  for  the  silo  wall  of  the 
desired  thickness  between  the  vertical  strips.  This 
can  be  made  longer,  and  then  holes  bored  in  same  so 
as  to  enable  the  worker  to  regulate  the  width  of  the 
wall  from  6"  to  12"  in  thickness,  or  more,  as  may  be 
desired,  thus  making  the  same  form  adaptable  to 
different  sizes  of  silos. 

The  long  strip,  shown  in  Fig.  3,  is  of  sufficient 
length  to  reach  entirely  across  the  diameter  of  the 
silo  and  then  lap  onto  the  vertical  strips,  to  which 
the  sheet  steel  is  attached  at  each  side.  Thus,  for  a 
silo  10 ',  inside  diameter,  this  piece  would  have  to  be 
12'  long,  to  permit  an  8"  wall  to  be  molded.  This 
strip  is  bolted  to  the  vertical  strips,  as  illustrated, 
and  also  bolted  to  the  clamp  upon  the  opposite  side 
of  the  silo. 


26  PRACTICAL  SILO  CONSTRUCTION 

As  the  weight  of  raising  the  forms  is  largely  upon 
these  pieces,  they  should  be  at  least  2x6"  and  of 
selected  wood,  so  that  they  will  not  bend  or  break 
from  the  strain. 

A  number  of  the  clamps  are  constructed  so 
that  they  will  hold  the  sheet  steel  to  the  true 
circle.  This  requires  less  where  the  24-gauge  steel 
is  employed  than  where  lighter  weight  sheets  are 
used. 

The  arrangement  of  the  clamps  and  braces  are 
shown  in  the  plan  of  one-half  of  silo  form,  at  Fig.  4, 
in  which  a  a  refers  to  the  central  vertical  upright 
used  to  raise  the  silo  form,  as  required;  b  b  is  the 
2x6"  strip  extending  across  the  top  of  the  silo  form,' 
by  which  it  is  raised;  c  c  are  the  guide-strips  em- 
ployed to  keep  the  silo  form  level  when  it  is  raised, 
and  also  when  the  weight  of  concrete  is  all  upon  one 
side  of  form;  d  d  illustrates  the  position  of  the  wood 
clamps  or  vertical  strips  attached  to  the  horizontal 
2x6"  strip,  as  explained  for  Fig.  3.  The  clamps 
designated  by  this  letter  at  the  quarter  segment  of 
silo  form  are  connected  to  the  main  horizontal  strip 
by  two  brace  rods,  //,  which  may  be  made  of  2x4" 
lumber,  bolted  to  the  clamp  and  also  to  the  sliding 
guides  c  c  at  center.  The  clamps  e  e,  shown  be- 
tween the  quarter  segments  of  circle  are  simply 
employed  to  keep  the  sheet  steel  to  the  true  circle. 
These  need  not  be  as  strong  construction  as  the 
clamps  placed  at  each  quarter  of  the  circle,  and  are 
held  from  spreading  or  warping  from  position  by 


[IP 


FIG.  3.— Wood  clamp  for  molding  monolithic  walls. 


28  PRACTICAL  SILO  CONSTRUCTION 

the  braces  g  g,  as  shown  in  plan.  The  number  of 
these  clamps  must  be  determined  by  the  diameter 
of  the  circle,  but  should  never  be  less  than  two, 
placed  between  each  clamp  at  the  quarter  segment 
of  circle;  nor,  when  the  24-gauge  sheet  steel  is  em- 
ployed, should  they  be  more  than  36"  apart  on  the 
outside  circumference  of  circle. 

The  strips  shown  at  h  h  in  Fig.  4,  cut  along  one 
edge  in  a  convex  form,  may  be  employed  to  keep 
the  sheet  steel  from  bending  under  the  weight  of 
the  concrete.  These  are  cut  in  the  proper  segment 
of  circle  so  that  they  will  fit  between  each  clamp, 
around  the  inside  circumference  of  your  circle. 
Those  shown  at  i  i  are  cut  in  a  concave  form  and  are 
fastened  to  the  outside  circumference  of  your  circle, 
between  clamps.  By  using  these  retaining  strips, 
or  pieces  of  strap,  iron  bent  into  the  same  form  and 
riveted  to  the  sheet  steel,  the  lighter  weight  steel 
may  be  employed.  Thus,  with  three  of  these  re- 
taining strips  between  each  clamp,  No.  28-gauge 
sheet  steel  has  been  successfully  employed  for  the 
forms  or  centering. 

The  value  of  employing  the  retaining  strips  and 
using  a  lighter  grade  of  sheet  steel  is  that  the  forms 
will  thus  be  made  lighter,  as  the  24-gauge  sheets 
weigh  about  17  pounds  to  the  sheet  of  24x101";  the 
26-gauge  weighs  13  pounds  to  the  sheet,  while  the 
27-gauge  weighs  111  pounds,  and  the  28-gauge 
weighs  but  10J  pounds  to  the  sheet.  This  is  also 
able  to  effect  a  saving  in  the  cost  of  the  forms,  as 


FIG.  4.— Plan  for  clamps  and  braces  used  with  wood  silo  forms. 


30 


PRACTICAL  SILO  CONSTRUCTION 


there  is  a  difference  of  20  cents  a  sheet  between  the 
28-gauge  and  the  24-gauge. 

The  following  table  shows  the  number  of  sheets 
of  steel  required  for  the  forms  or  centering  for 
various  diameters  of  silos,  with  the  approximate 
circumference  of  the  inside  form  or  core,  also  the 
number  of  wood-clamps  demanded  for  the  forms  to 
insure  their  being  held  rigidly  in  position. 

TABLE  III 

STEEL  SHEETS  REQUIRED 


Inside 
Diameter 
Silo. 

Inside 
Circumference 
Core. 

Number 
of  Sheets 
for  Core. 

Number 
Sheets 
Outside, 
6  "Wall. 

Number 
Sheets 
Outside, 
8  "Wall. 

Number 
Sheets 
Outside, 
10  'Wall. 

Clamps 
Required 
for  Form. 

10' 

31  '  4  " 

4 

4 

5 

5 

12 

12  ' 

37  '  6" 

5 

5 

5 

6 

12 

14' 

44'  0" 

6 

6 

6 

7 

12 

15' 

47'  1" 

6 

7 

7 

7 

16 

16' 

50'  2" 

7 

7 

7 

7 

16 

18' 

56'  6" 

8 

8 

8 

8 

20 

20' 

62  '  8  " 

8 

9 

9 

9 

20 

i 

If  no  other  means  for  bending  the  sheet  steel  to 
the  required  curve  are  at  hand  it  may  be  placed  over 
a  round  stick  of  at  least  6"  in  diameter,  and,  by 
fastening  one  end  securely  and  exerting  pressure 
upon  the  opposite  end  of  sheet,  it  can  be  bent  to 
conform  to  the  desired  curve.  The  above  table 
shows  the  number  of  the  usual  sized  sheets  to  order 
for  both  outside  and  inside,  or  core  form.  These  are 
bent  to  the  desired  curve  and  then  cut  so  to  have 
the  form  meet  exactly  at  the  four  quarters  of  the 
circle.  By  thus  making  the  centering  in  four  quar- 


PRACTICAL  SILO  CONSTRUCTION  31 

ter  segments  of  a  circle  they  are  the  easier  taken 
down  and  assembled  again.  Where  the  diameter  of 
silo  is  18'  or  20'  the  forms  can  be  built  in  one- 
eighths,  or  segments  equal  to  one-eighth  of  the  entire 
circumference  of  circle,  thus  making  the  weight  of 
each  section  less  than  if  made  in  quarters.  The 
segments  or  sections  are  bolted  together,  when  in 
use,  by  bolts  through  the  two  clamps,  that  join  to- 
gether at  the  point,  where  each  segment  joins  onto 
the  next  section.  Thus,  by  placing  a  clamp  at  both 
ends  of  each  section,  whether  quarter  sections  or 
eighths,  the  joining  of  sections  is  a  simple  matter 
of  bolting  the  clamps  together,  making  the  work  of 
assembling  the  forms  a  very  easy  and  simple  job. 

The  method  of  bolting  these  wood-clamps  to- 
gether is  shown  by  the  position  of  the  clamps  at  d  d 
in  Fig.  4,  and  also  by  the  holes  in  clamps  shown  in 
Fig.  3,  thus  making  a  simple  and  easily  operated 
method  of  securing  the  joints.  As  the  sheet  steel 
can  be  bent  slightly,  the  forms  may  be  built  to  be 
adjustable  to  many  different  sizes  of  silos.  Thus,  if 
the  forms  are  erected  for  a  10 '  silo,  using  4  sheets 
for  the  core  form  and  5  sheets  for  the  outside  form, 
the  steel  centering  is  attached  to  clamps  with 
screws,  placed  through  holes  punched  in  the  steel 
sheets.  Then,  to  adjust  to  a  12'  silo,  you  would  only 
have  to  add  a  portion  of  one  steel  sheet  to  the  core 
and  outside  form  and  adjust  the  clamps  around  this 
new  size  of  circle.  This  makes  it  easily  possible  to 
erect  any  diameter  of  silo  with  the  one  set  of  clamps 


32  PRACTICAL  SILO  CONSTRUCTION 

and  steel  centering  by  adding  or  removing  sections 
to  make  up  the  desired  circumference. 

Where  it  is  desired  to  erect  an  8  "  or  10  "  wall  for 
a  portion  of  the  height,  finishing  with  a  6"  wall, 
two  sections  of  the  form  are  fitted  with  steel  sheets 
to  make  the  desired  circumference.  Then,  when  the 
thickness  of  wall  is  to  be  reduced,  the  clamp  is 
slipped  along  the  length  of  these  sheets,  allowing 
the  surplus  length  of  sheet  to  lap  over  onto  the  one 
that  joins  to  same,  thus  reducing  the  circumference 
of  circle  to  mold  a  wall  of  the  required  thickness. 
This  leaves  a  mark  of  mold  or  indentation  upon  two 
sides  of  silo,  where  the  sheets  lap;  but,  as  this  is 
slight  it  will  not  be  a  serious  defect  to  the  work. 

METHOD    OF   RAISING    FORMS 

The  method  of  raising  the  forms  after  each 
course  is  placed  is  shown  at  Fig.  5,  as  well  as  a 
cross-section  of  wall  and  the  molding  form  or  cen- 
tering. The  vertical  post  shown  at  a  a  is  made  of 
two  2x8"  strips,  placed  together  with  a  space  be- 
tween them  of  2",  so  as  to  permit  the  braces  b  b  to 
slide  between  same  as  the  silo  forms  are  raised. 
The  two  vertical  strips,  c  c,  are  guides  that  are 
bolted  to  the  horizontal  braces  b  b,  and  by  press- 
ing against  the  vertical  posts  a  a  the  silo  form  is 
kept  from  tipping  to  one  side;  nor  is  it  allowed  to 
be  raised  higher  at  one  side  than  the  other.  This  is 
a  most  important  feature,  and  these  guides  should 
never  be  left  off  the  form,  otherwise  you  will  have 


*£t 

',?*.' 

•"./ 

^v\ 


**  i^- 
'». 


// 


/,'r. 


II 
tf 


\ 


\ 

\\ 
v\ 
\\ 


L.,  1 


Li 


FIG.  5. — Sectional  view  of  silo  forms  in  operation. 


34  PRACTICAL  SILO  CONSTRUCTION 

no  assurance  that  the  form  will  not  be  raised  higher 
upon  one  side  than  upon  the  opposite  side  of  silo, 
thus  throwing  the  wall  from  the  vertical  line  or 
plumb.  With  every  silo  form  heretofore  explained, 
this  feature  has  never  been  given  attention;  and  its 
importance  is  apparent  to  any  one  at  a  glance,  as  it 
insures  a  perfect  wall  without  the  bother  of  leveling 
the  form  each  time  after  raising.  The  clamps  at 
sides  are  shown  by  d  d;  and,  as  the  same  designating 
letters  are  given  to  each  part  in  Fig.  5  as  in  Fig.  4, 
it  is  an  easy  matter  to  understand  the  invaluable 
and  important  features  of  this  simple  and  easily 
constructed  silo  form. 

The  tackle  used  to  raise  the  forms  is  shown  by 
the  dotted  lines  in  Fig.  5.  The  wire  cable,  or  ropes, 
pass  down  upon  one  side  of  the  posts,  in  center,  to  a 
drum  or  roller  at  the  bottom  of  same.  This  drum  is 
fitted  with  a  ratchet-wheel  and  pawl,  to  lock  the 
drum  at  any  point  desired,  also  with  two  arms,  or 
cranks,  for  moving  the  drum.  Hence,  with  two  men, 
the  form  is  very  easily  raised  each  time  in  a  far 
more  simple  and  desirable  manner  than  by  wire 
loops  over  levers,  which  do  not  raise  the  forms 
evenly,  and  consequently  require  greater  effort,  with 
danger  of  breaking  out  pieces  of  the  concrete  wall. 

The  vertical  posts  in  center  of  Fig.  5  are  braced 
at  the  bottom  by  horizontal  pieces  bolted  to  same. 
This  is  made  so  as  to  have  ample  bearing  surface 
upon  the  ground,  so  the  weight  of  forms  will  not  cause 
it  to  sink  or  bury  into  the  earth  at  one  side,  and  thus 


PRACTICAL  SILO  CONSTRUCTION  35 

draw  the  wall  from  the  vertical  or  plumb  line.  With 
this  form  of  post  the  concrete  floor  may  be  laid  in  the 
bottom  of  the  silo,  and  the  uprights  set  upon  same 
without  injury.  By  keying  or  bracing  this  securely 
at  the  bottom,  and  staying  the  top  of  the  post  with 
guy  wires,  the  walls  of  silo  must  be  built  absolutely 
plumb,  for  the  forms  cannot  be  raised  in  any  other 
manner.  This  "fool-proof"  feature  will  be  of  in- 
terest to  the  contractor  who  must  intrust  his  work 
to  others ;  and,  as  mistakes  in  this  work  are  costly, 
every  safeguard  against  errors  is  of  great  impor- 
tance. 

This  style  of  form  permits  the  placing  of  any  re- 
inforcement desired.  The  upright  rods  are  placed 
with  the  first  course  of  concrete,  spacing  them  the 
proper  distance  apart.  These  are  held  in  a  vertical 
position  by  braces  nailed  to  the  top  of  the  center 
posts  until  the  wall  has  advanced  enough  to  hold 
them  securely.  Then  the  braces  can  be  removed,  to 
finish  the  silo. 

By  nailing  short  strips  to  the  center  posts,  hori- 
zontally, a  ladder  can  be  made  for  convenience  in 
reaching  the  forms  at  every  stage  of  the  construc- 
tion. 

USING  AUTOMATIC   CLAMP 

The  illustration  at  Fig.  6  shows  the  use  of  the 
automatic  wall-clamp,  explained  in  CONCRETE  WALL 
FORMS  of  this  series,  as  adapted  to  silo  work.  This 
permits  the  molding  of  a  hollow  wall  with  a  continu- 


FIG.  6.— Using  automatic  wall-clamp,  as  explained  in 
CONCEETE  WALL  FORMS,  for  silo  work. 


PRACTICAL  SILO  CONSTRUCTION  37 

ous  air-chamber  between  the  walls,  a  feature  that  is 
an  absolute  preventative  against  freezing  of  the 
silage. 

These  wall-clamps  are  constructed  of  strap  iron, 
and  may  be  built  by  any  one  at  a  slight  cost.  The 
steel  sheets  are  bolted  or  riveted  to  the  clamps  as 
shown  in  Fig.  6,  and  each  section  is  then  bolted  to- 
gether or  fastened  with  a  small  clamp,  if  the  sec- 
tions are  to  be  raised  separately.  The  core  form 
collapses  when  the  center-bar  with  handle  is  raised. 
This  same  operation  causes  the  outside  forms  to 
draw  away  from  the  concrete  wall,  thus  freeing  the 
form  from  the  concrete  at  all  points. 

When  the  form  is  again  lowered  into  position  the 
core  is  pressed  outward  to  its  proper  place,  and  the 
outside  forms  drawn  in  to  the  correct  circumference. 
The  simple  act  of  lowering  the  form  automatically 
locks  it  into  position  for  filling,  while  the  small 
metal  bars  at  the  bottom  of  the  center-bar  engage 
with  the  concrete  wall  and  prevent  the  centering 
from  slipping  down. 

The  sections  are  reinforced  with  bars  of  strap 
iron  riveted  to  the  sides  of  the  steel  sheets,  as  shown 
in  illustration,  thus  holding  them  to  the  true  circum- 
ference of  the  circle. 

The  easiest  method  of  using  this  style  of  form  is 
not  to  have  more  than  two  or  three  clamps  to  each 
section,  thus  making  the  sections  quarters  or  eighths 
of  the  circumference  of  the  silo.  These  sections 
are  raised  separately  by  removing  the  small  clips  or 


38  PRACTICAL  SILO  CONSTRUCTION 

clamps  holding  the  sections  together.  Each  section 
can  be  raised  and  then  the  segments  or  sections 
again  fastened  together,  avoiding  the  use  of  any 
tackle  to  raise  the  forms  after  each  course,  as  two 
men  can  lift  the  sections  from  the  staging  erected 
for  the  workmen  in  placing  the  concrete. 

By  having  small  segments  or  sections  the  forms 
can  be  employed  for  many  sizes  of  silos,  by  adding 
or  removing  a  section  as  demanded,  which  is  a  valu- 
able feature  to  the  contractor  who  must  build  all 
sizes  of  silos. 

PLASTERED    SILOS 

A  successful  type  of  silo  construction  has  been 
recently  used;  and  that  it  is  exceedingly  practical  is 
shown  by  the  illustration  at  Fig.  7,  which  illustrates 
the  method  of  arranging  the  vertical  and  horizontal 
reinforcement  and  also  the  use  of  the  wire  lath  that 
is  attached  to  same. 

This  type  of  silo  construction  employs  the  placing 
of  §  "  vertical  rods  around  the  circumference  of  silo, 
ground  plan,  as  per  the  spacing  for  diameter  given 
in  Table  IV.  To  this  is  added  the  horizontal  or 
"hoop"  reinforcement,  using  §"  rods,  and  spacing 
them  as  instructed  in  Table  V.  These  horizontal 
rods  are  tied  with  wire  to  the  vertical  rods  at  each 
point  they  intersect,  thus  making  a  skeleton  or  "bal- 
loon" frame  of  the  silo. 

The  vertical  and  horizontal  rods  are  placed  so 
that  they  will  be  about  1J "  from  the  outside  of  the 


FIG.  7.— Method  of  constructing  plastered  silos. 


40  PRACTICAL  SILO  CONSTRUCTION 

completed  wall,  which  is  usually  made  about  3J" 
in  thickness. 

After  the  framework  of  rods  are  in  place,  sheets 
of  wire  lath,  or  expanded  metal  lath,  are  fastened  to 
the  rods  by  tying  with  wire  at  each  intersection  of 
the  rods  and  also  at  the  joints  of  the  metal  lath,  so 
that  the  sheets  are  securely  fastened  to  the  frame- 
work, and  thus  make  a  reinforcement  that  will  be 
ample  to  resist  the  pressure  of  the  silage,  also  the 
strain  placed  upon  the  silo  from  other  causes. 

The  concrete  is  then  plastered  upon  the  inside  of 
the  silo  to  an  average  thickness  of  2",  and  while  this 
is  damp  enough  to  insure  a  good  bond  the  plaster 
coat  is  then  placed  upon  the  outside  of  the  metal  lath. 
The  methods  followed  in  stucco  work  are  of  use  in 
this  system  to  insure  a  good  bond  between  the  two 
coats  of  concrete  plaster  applied. 

The  door-frames  are  inserted  in  spaces  left  for 
same  as  the  work  progresses.  By  having  a  groove 
on  the  outside  of  the  door-frame  into  which  the 
metal  lath  will  fit,  the  frames  are  securely  held  in 
position.  The  roof  is  placed  by  having  the  | "  rods 
extend  several  inches  above  the  top  of  silo,  and  these 
are  threaded  for  a  nut.  Thus  the  rafters  are  bolted 
to  the  vertical  rods  that  form  a  part  of  the  reinforce- 
ment of  the  structure. 

This  system  of  construction  is  far  in  advance  of 
the  method  of  using  a  wood  frame,  to  which  wood 
lath  are  nailed  and  the  entire  surface  coated  with 
concrete  plaster  coats. 


PRACTICAL  SILO  CONSTRUCTION  41 

The  plastered  silo  may  be  constructed  with  a  con- 
tinuous air-chamber  by  attaching  the  wire  lath  to 
the  outside  and  also  to  the  inside  of  the  |"  rods. 
By  plastering  upon  each  side  a  space  is  left  between 
the  plaster  coats  that  is  a  preventative  against  frost 
in  the  silo. 

CONCRETE    BLOCK   SILOS 

Silos  of  concrete  blocks,  or  units,  have  been  em- 
ployed so  generally  that  a  description  of  this  type  of 
construction  is  not  needful  to  the  average  concrete 
contractor.  The  manufacturers  of  concrete  block 
machines  put  out  a  silo  block  machine  for  molding 
hollow  building  blocks  for  any  diameter  of  silo,  thus 
making  the  construction  of  the  units  the  same  as  the 
manufacture  of  building  blocks  for  any  type  of  wall. 

For  the  man  who  desires  to  make  his  own  blocks, 
the  type  of  mold  shown  in  Fig.  8  is  of  value,  as  this 
molds  a  wet  process  hollow  block.  The  molds  are 
easily  constructed  by  using  two  planks  for  the  sides. 
In  width  these  should  be  about  2"  more  than  the  de- 
sired width  of  block  (or  thickness  the  wall  is  to  be) 
at  the  points  where  the  desired  height  of  each  block 
is  measured.  The  planks  are  cut  with  a  saw  kerf 
for  3  "  in  depth.  These  are  to  receive  the  sheet  iron 
dividing  plates  between  the  blocks,  as  illustrated. 
A  convex  form  is  built  for  the  bottom  of  mold  from 
wood  strips,  cut  into  the  proper  curve  for  the  seg- 
ment of  circle  the  block  is  to  take,  on  the  inside  of 
silo.  These  strips  are  covered  with  sheet  iron,  and 


FIG.  8.— Mold  for  silo  blocks,  wet  process. 


PRACTICAL  SILO  CONSTRUCTION  4& 

the  form  constructed  to  make  a  bottom  for  the  en- 
tire length  of  the  mold. 

The  sheet  iron  dividing  plates  are  cut  in  the  con- 
vex and  concave  form  shown  in  Fig.  9,  at  top.  The 
length  is  equal  to  the  length  of  the  block,  plus  4 "  at 
each  end  for  inserting  in  the  saw  kerf  and  for  a  hole 
in  the  ends  for  putting  an  iron  pin  into,  to  hold  the 
side  forms  or  planks  tightly  up  against  the  "  shoul- 
der" cut  upon  the  dividing  plate. 

A  beveled  or  triangular  strip  of  wood  is  now  cut 
of  the  exact  length  of  the  block.  This,  by  soaking 
in  water,  can  be  bent  to  the  curve  of  the  block,  and 
is  then  nailed  to  the  top  of  the  dividing  plate,  or 
about  li  "  from  the  top,  as  shown  in  the  illustration 
at  Fig.  9.  This  molds  a  groove  in  the  silo  block  for 
the  placing  of  the  hoops  or  wires  used  as  reinforcing 
material.  This  groove  is  shown  in  the  completed 
block  at  Fig.  9. 

Below  the  triangular  strip,  round  holes  are  cut 
for  inserting  lengths  of  gas-pipe,  which  mold  the 
hollow  spaces  in  the  blocks.  These  pipes  are  well 
greased  when  the  mold  is  assembled  and  also  slightly 
flattened  at  one  end,  into  which  a  key  or  crank  is 
placed  for  turning  the  pipe  around  before  removing 
same  from  the  completed  series  of  blocks.  This  is 
necessary,  as  otherwise  the  pipes  could  not  be  as 
easily  drawn;  but,  by  breaking  the  bond,  if  any,  be- 
tween the  pipes  and  concrete,  they  are  withdrawn 
quite  easily. 

Two  of  the  dividing  plates  are  used  between  each 


FIG.  9.— Sheet  iron  dividing  plate  and  completed  silo  block. 


PRACTICAL  SILO  CONSTRUCTION  45 

block,  or  one  dividing  plate  with  a  triangular  strip 
upon  each  side,  so  as  to  mold  the  channel  or  groove 
for  wires  into  both  sides  of  block. 

The  form  is  now  assembled  in  the  manner  illus- 
trated in  Fig.  8,  and  the  concrete  placed  in  the 
mold,  finishing  the  top  with  the  trowel,  or  using  a 
template  of  the  desired  curve.  The  concrete  is  placed 
wet  and  the  blocks  allowed  to  cure  in  the  mold,  when 
the  iron  pins  through  dividing  plates  can  be  drawn 
and  the  side  planks  removed,  thus  releasing  the  en- 
tire series  of  blocks,  which  can  be  as  many  as  the 
length  of  plank  will  accommodate. 

The  wood  portions  of  this  mold  should  be  well 
treated  to  several  coats  of  shellac  or  oil  paint,  so  as 
to  prevent  the  moisture  in  the  concrete  from  warping 
the  wood.  The  concrete  is  placed  wet;  thus  a  dense 
block  is  obtained  with  but  little  tamping. 

The  method  of  laying  the  blocks  is  shown  in  Fig. 
10,  also  the  usual  manner  of  securing  the  door  open- 
ings. 

While  not  necessary,  a  wire  hoop  can  be  placed  in 
each  course  of  blocks  in  the  groove  or  channel  for 
that  purpose.  This  will  bring  the  reinforcement  the 
height  of  the  block  apart.  Thus,  if  a  block  7J  "  high 
is  employed  the  reinforcement  should  be  ample  for 
any  strain  it  will  be  required  to  withstand.  This 
can  be  placed  in  each  second  course  of  blocks  for  the 
5 '  of  distance  from  the  top  of  the  silo  downward, 
if  No.  5  wires  are  used  for  the  wire  hoops,  and 
make  the  wall  of  ample  strength. 


FIG.  10. — Reinforcing  block  silos  and  molding  door-openings. 


PRACTICAL  SILO  CONSTRUCTION  47 

For  the  door-openings  a  double  length  block  is 
constructed,  as  shown  in  illustration.  This  should 
be  of  the  proper  curve  to  conform  to  the  circumfer- 
ence of  circle,  and  also  be  reinforced  with  at  least 
three  § "  rods  placed  horizontally  in  same.  Two  of 
these  rods  are  placed  within  about  1 "  of  the  bottom  of 
block,  which  forms  the  upper  part  of  the  door-frame ; 
the  third  rod  is  placed  about  3"  above  this,  and  may 
be  further  strengthened  by  short  stirrup  rods  con- 
necting the  horizontal  reinforcement.  The  door- 
frames may  be  set  in  position  as  the  blocks  are 
placed;  and,  by  attaching  to  the  reinforcement  of 
the  silo,  the  frames  are  thus  held  rigidly  in  posi- 
tion against  the  pressure  of  the  silage. 

At  Fig.  11  is  shown  a  plan  of  laying  the  silo 
blocks  so  as  to  make  a  continuous  door-opening  from 
top  to  bottom  of  the  silo.  The  blocks  are  molded  or 
cut  at  the  point  they  intersect  at  the  door-opening 
so  as  to  lock  in  the  manner  shown.  This  can  be  accom- 
plished by  using  a  block  of  wood  set  vertical  in  one 
end  of  the  mold  used  for  these  blocks,  and  thus  saving 
the  labor  of  cutting  each  block  to  join  in  this  manner. 

The  reinforcing  wires  are  bent  to  form  a  contin- 
uous reinforcement  or  bond  to  the  end  of  the  door- 
opening. 

In  constructing  the  blocks  for  a  known  size  or 
diameter  of  silo  it  is  an  easy  matter  to  make  them 
of  a  length  so  that  it  requires  a  certain  number  of 
blocks  to  make  the  exact  circumference.  Then,  by 
molding  a  number  of  half  blocks,  the  joints  may  be 


FIG.  11. — Ground  plan  of  silo  with  continuous  door-opening. 


PRACTICAL  SILO  CONSTRUCTION  49 

broken  in  each  course  laid,  and  the  work  of  laying 
greatly  simplified.  This  can  also  be  arranged  so  as  to 
bring  the  hollows  or  holes  in  blocks  made  by  the  gas- 
pipe  exactly  over  those  in  the  block  below,  thus  per- 
mitting vertical  reinforcement,  if  so  desired. 

CONCRETE    FOB   SILO    WORE 

For  the  manufacture  of  silo  blocks  or  monolithic 
silo  walls  the  usual  mixture  is  1:2:4,  using  clean, 
sharp  sand  that  is  well  graded,  and  crushed  stone  or 
coarse  gravel  for  the  larger  aggregate.  This  should 
not  be  over  J "  in  diameter.  The  materials  call  for 
thorough  mixing  and  enough  moisture  to  completely 
wet  the  mix.  This  makes  it  impossible  to  raise  the 
forms  until  the  concrete  placed  has  had  time  to 
harden  or  set.  While  this  may  seem  a  hardship  to 
the  contractor  in  a  hurry,  it  is  the  one  and  only  safe 
policy,  even  when  a  semi-dry  mixture  is  employed. 
Many  jobs  are  injured  by  haste  in  construction ;  for, 
if  the  concrete  has  not  had  from  24  to  36  hours  to 
harden,  even  under  the  most  favorable  conditions  it 
is  a  menace  to  the  workmen  employed  on  any  job 
where  the  concrete  must  support  the  staging  or  scaf- 
fold. Where  the  forms  can  be  filled  in  a  few  hours 
or  one-half  a  day,  the  concrete  can  easily  be  given 
24  hours  to  harden  without  delaying  the  work. 

Where  the  mixture  is  made  semi-dry  it  must  be 
tamped  very  solidly ;  but  in  the  event  of  a  wet  mix- 
ture the  tamping  can  be  replaced  by  placing  the 
mixture  in  thin  layers  or  courses  and  pressing  it  out 


50  PRACTICAL  SILO  CONSTRUCTION 

against  the  forms  or  "puddling."  The  wet  mix  will 
thus  pack  more  solidly  than  a  semi-dry  mix  well 
tamped,  hardening  with  equal  speed  under  favorable 
conditions,  and  giving  a  smoother  and  more  perfect 
finish  to  the  surface  of  walls. 

The  composition  usually  employed  for  plastered 
silos  is  the  same  as  that  used  for  stucco;  and  often 
a  small  amount  of  plastering  hair  is  added  to  the 
mixture.  Where  lime  is  added  to  the  mix  the 
usual  proportions  are  2:5:1,  cement,  sand,  and  lime. 
Without  the  addition  of  lime  the  best  proportion  is 
1:2J,  using  well-graded  sand,  although  a  proportion 
of  1:3  has  been  employed  with  success.  The  use  of 
lime,  either  the  hydrated  lime  as  sold  almost  exclu- 
sively to-day  or  the  cream  of  lime  prepared  by  the 
plasterer  as  needed,  is  of  advantage  in  the  concrete, 
as  it  gives  it  great  plasticity  and  lightens  the  work 
of  spreading  to  a  large  extent. 

REINFORCEMENT   OP   SILOS 

The  question  of  reinforcement  is  an  important 
one  to  the  silo  builder;  and  in  planning  and  placing 
the  steel  every  precaution  should  be  taken  to  pre- 
vent a  weak  point  in  the  work. 

At  Fig.  12  is  shown  a  type  of  reinforcement  that 
employs  vertical  |"  rods  around  the  wall  of  silo, 
except  upon  each  side  of  the  door-openings,  where 
the  rods  are  replaced  by  2"  angle  irons  or  bars. 
These  are  connected  together  between  each  door- 
opening  with  a  horizontal  bar  of  the  same  material 


FIG.  12.— Silo  reinforcement  and  method  of  placing. 


52 


PRACTICAL  SILO  CONSTRUCTION 


bolted  to  the  uprights.  The  hoops  or  wires  extend- 
ing horizontally  around  the  silo  wall  are  tied  to  the 
angle  bars,  thus  forming  a  continuous  reinforcement 
entirely  over  the  wall  of  silo.  By  referring  to  the 
drawing  at  Fig.  12  the  advantages  of  this  type  of 
reinforcement  is  easily  seen ;  and,  as  it  is  simply  con- 
structed, there  is  nothing  to  prevent  its  general  use. 
For  the  vertical  reinforcing  rods  there  is  nothing 
as  satisfactory  as  those  of  !"  in  diameter.  These 
weigh  .375  of  a  pound  to  the  foot;  and,  when  spaced 
around  the  circumference  of  the  silo,  as  explained  in 
the  following  table,  make  a  reinforcement  that  will 
support  its  own  weight  and  the  reinforcement  added 
to  same  without  bending  or  becoming  displaced,  as 
is  usually  the  trouble  with  vertical  reinforcement 
formed  of  wires. 

TABLE   IV 

VERTICAL  REINFORCEMENT  AND  SPACING  f  "  RODS. 


Height  of  Silo 
in  Feet. 

To  25'. 

To  30'. 

To  35'. 

To  40  '. 

No. 

Space. 

No. 

Space. 

No. 

Space. 

No. 

Space. 

10  '  to  14  '  Diam. 
14  'to  17  '  Diam. 
18  '  to  20  '  Diam. 

1 
1 

30" 

28" 

1 
1 

19  " 
24" 

2 
1 
1 

26" 
17" 
20" 

2 
2 
1 

19" 
27" 

17" 

The  height  of  silo  is  given  in  the  first  line,  and 
the  number  of  rods  to  use,  spaced  at  the  proper  dis- 
tance apart,  in  the  second  line.  Thus,  in  a  silo  10 ' 
in  diameter  and  25' high,  one  f"  rod  is  used  for 


PRACTICAL  SILO  CONSTRUCTION 


53 


vertical   reinforcement,    each  30 "  of    the   distance 
around  the  circumference; 

The  horizontal  reinforcement  may  be  rods  or 
wires  (where  rods  are  used  the  most  satisfactory  are 
those  I"  in  diameter),  while  No.  5  and  No.  8  wire  is 
usually  employed  for  the  horizontal  hoops,  as  they 
are  easier  bent  to  the  proper  circle  than  §  "  rods. 


TABLE   V 

SPACING  HORIZONTAL  REINFORCEMENT  OR  HOOPS. 
Distance  Measured  from  Top  of  Silo  in  5'  Spaces 


1-5'. 

2-5'. 

3-5'. 

4-5'. 

5-5'. 

6-5'. 

7-5'. 

8-5'. 

Diameter 

Size  of  Rods  or 

Silo  Inside. 

Wires  Used. 

N.-S. 

N.-S. 

N.-S. 

N.-S. 

N.-S. 

N.-S. 

N.-S. 

N.-S. 

10'—  14'  

1-18" 

1-18" 

1-15" 

1-14" 

1-11" 

1-9" 

1-8" 

1-7" 

|"rods 

10'—  14'  

1-16" 

1-11" 

1-8" 

1-  6" 

2-  9" 

2-7" 

2-6" 

2-5" 

No.  5  wire 

10'—  14'  

1-12" 

1-7" 

2-9" 

3-9" 

3-  8" 

3-7" 

3-6" 

3-5" 

No.  8  wire 

14'—  17'  

1-18" 

1-18" 

1-14" 

1-11" 

1-9" 

1-7" 

1-6" 

1-5" 

|"rods 

14'—  17'  

1-12" 

1-  9" 

1-6" 

2-8" 

2-7" 

2-5" 

3-7" 

3-6" 

No.  5  wire 

14  '-17'  

1-11" 

1-  5" 

2-  7" 

3-8" 

3-  6" 

3-5" 

3-5" 

3-4" 

No.  8  wire 

18'—  20'  

1-18" 

1-18" 

1-12" 

1-  9" 

1-7" 

1-6" 

1-5" 

1-4" 

i'rods 

18  '_  20'  

1-12" 

1-7" 

2-  9" 

2-7" 

3-8" 

3-7" 

3-6" 

3-5" 

No.  5  wire 

18'-20'  

1-9" 

2-  9" 

3-9" 

3-  6" 

3-5" 

3-4" 

3-3" 

3-3" 

No.  8  wire 

The  distance  from  the  top  is  measured  in  spaces 
of  5'.  Thus,  in  the  first  line,  1-5'  refers  to  the  first 
5  feet  from  top  o±  silo  downward;  2-5'  is  the  second 
5';  3-5'  is  the  third  5';  or  15'  from  top  of  silo,  and 
in  this  manner  to  the  distance  to  8-5 ',  or  40  feet, 
measured  downward  from  top  of  silo.  The  great- 
est pressure  is  at  the  bottom  of  silo,  the  silage  ex- 


54  PRACTICAL  SILO  CONSTRUCTION 

erting  a  side  pressure  of  about  11  pounds  to  each 
square  foot,  for  every  foot  of  depth. 

In  the  next  line  N.  refers  to  the  number  of  rods 
or  strands  of  wire  used  for  each  hoop  or  horizontal 
reinforcement.  S.  refers  to  the  distance  in  inches 
these  hoops  or  horizontal  reinforcements  are  spaced 
apart.  The  first  column  states  the  inside  diameter 
of  the  silo,  while  the  last  column  states  the  size  of 
the  wire  or  rods  used. 

Thus,  for  a  silo  10  'to  14 '  in  diameter  we  would 
use  1,  | "  rod,  spaced  18  "  apart  for  the  first  5 '  from 
the  top,  also  for  the  next  5 '  to  10 ' ,'  15  "  apart  for  10 ' 
to  15',  14 "  apart  for  15'  to  20',  11 "  apart  for  20'  to 
25 ',  9  "  apart  for  25 '  to  30 ',  8  "  apart  for  30 '  to  35 ', 
and  7  "  apart  for  35 '  to  40 ',  thus  bringing  the  great- 
est strength  of  the  reinforcement  at  the  bottom  of 
the  silo,  where  the  greatest  pressure  is  exerted  by 
the  column  of  silage. 

The  hoops  or  horizontal  reinforcement  should  be 
tied  to  the  vertical  rods  with  wire.  These  may  be 
added  as  the  forms  are  filled  and  raised,  so  they  will 
not  interfere  with  the  clamps  used  on  the  forms. 

The  system  of  reinforcing  given  is  ample  for  a 
wall  of  6"  in  thickness  or  greater  when  made  mono- 
lithic, or  it  may  be  applied  to  plastered  silos  where 
the  wire  lath  or  expanded  metal  lath  is  securely  tied 
to  the  reinforcing  wires  and  rods. 


PRACTICAL  SILO  CONSTRUCTION  55 

DOORS    FOR   THE    SILO 

The  usual  size  of  silo  door  is  24x30",  and  in  some 
types  of  construction  the  height  has  been  increased  to 
36  ".  The  door  should  be  amply  large  so  as  to  permit 
the  easy  removal  of  the  silage,  yet  if  made  too  large 
there  will  be  a  weak  point  in  the  wall  by  the  exces- 
sively large  opening.  For  a  door  24  x  30  "  they  should 
be  spaced  5 '  6 "  apart,  center  to  center,  on  the  wall 
of  silo,  beginning  at  a  point  about  3 '  from  the  bot- 
tom on  a  silo  with  floor  at  ground-level  and  about 
18"  above  ground-level,  on  a  silo  where  the  floor  is 
below  ground-level. 

At  Fig.  13  is  shown  two  types  of  silo  doors.  That 
at  a  has  a  channel  or  groove  molded  upon  the  inside 
of  the  silo  wall,  into  which  one  side  of  the  silo  door 
fits  tightly.  The  door  is  built  of  an  outer  and  inner 
sheathing  of  tongued  and  grooved  lumber,  nailed  to 
4  or  6  cleats  of  2x4"  lumber,  which  are  in  length 
equal  to  the  width  of  the  door.  The  door  shown  at 
a  fits  tightly  into  the  opening;  and,  with  strips  of  tar 
paper  inserted  around  between  door  and  frame,  the 
joint  is  made  air-tight. 

The  type  of  door  shown  at  b  (Fig.  13)  is  made  of 
the  tongued  and  grooved  lumber  nailed  to  the  2x4" 
cleats  upon  each  side.  This  door  is  beveled  upon  all 
four  sides ;  and  when  drawn  tight  with  the  bolt  and 
cross-bar,  with  strips  of  tar  paper  around  same,  the 
joint  cannot  but  be  air-tight.  Care  should  be  used 
to  make  the  doors  so  that  they  fit  perfectly,  as  other- 


FIG.  13.— Sectional  view  of  two  styles  of  silo  doors. 


PRACTICAL  SILO  CONSTRUCTION     .  57 

wise  the  silo  cannot  be  absolutely  air-tight;  and 
unless  so  the  results  will  not  give  satisfaction. 

The  view  of  door  shown  in  Fig.  14  illustrates  the 
cross-bar  or  2x4"  strip,  which  is  cut  3'  long  and 
bolted  to  the  center  of  door.  This  strip  rests  against 
the  walls  of  silo  on  each  side  of  the  door-openin'g. 
Thus,  by  tightening  the  nut  on  the  bolt,  the  door  is 
drawn  closely  into  the  frame  or  opening  for  same. 

The  dotted  lines  in  Fig.  14  show  how  the  rein- 
forcement should  be  placed  at  the  point  where  each 
door-opening  will  come  in  the  silo  wall.  Two  I" 
rods  are  used  upon  each  side  of  the  opening,  and 
these  are  placed  so  that  they  are  within  1J "  of  the 
surface  of  concrete  around  the  door-frame.  The 
pressure  exerted  against  the  silo  wall  at  this  point, 
by  drawing  the  doors  into  position,  makes  this  pre- 
caution of  ample  reinforcing  an  important  one  for 
the  builder  who  desires  durability  in  construction, 
even  in  monolithic  silos  with  heavy  walls.  This  re- 
inforcement is  necessary  where  plastered  silos  are 
constructed,  as  the  thickness  of  wall  is  not  enough 
to  withstand  the  pressure  exerted  by  drawing  the 
doors  into  position  with  the  bolt,  unless  strongly 
reinforced. 

A  continuous  door  for  the  silo  is  shown  in  the 
illustration  at  Fig.  15.  The  forms  are  built  to  mold 
this  opening  of  the  desired  width,  which  is  usually 
the  same  upon  the  inside  as  the  width  of  the  silo 
door.  The  thickness  of  these  wing  walls  is  best 
made  the  same  as  the  walls  of  silo,  which  will  avoid 


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1  1 
1  1 

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FIG.  14. — Silo  door  and  reinforcement  for  opening. 


FIG.  15.— Continuous  door  in  concrete  silo. 


60  PRACTICAL  SILO  CONSTRUCTION 

having  a  separate  form  to  mold  same.  The  opening 
is  closed  by  using  short  lengths  of  tongued  and 
grooved  planks,  supplemented  with  a  thickness  of 
tar  paper  behind  same.  Two  thicknesses  of  these 
planks  are  employed,  one  at  the  outside  opening  of 
the  door,  with  the  other  at  the  opening  upon  the 
inside  of  silo.  The  latter  depends  upon  the  pressure 
of  silage  to  hold  them  in  place  and  are  placed  as 
the  silo  is  filled. 

The  outside  planks  are  held  in  place  by  2x4" 
strips  bolted  to  the  concrete  walls,  the  bolts  for  same 
being  imbedded  in  the  concrete  as  the  material  is 
placed  in  form. 

SILO   HOOFS 

A  successful  type  of  silo  roof,  using  concrete  as 
the  covering  material,  is  shown  at  Fig.  16.  The 
rafters  are  cut  to  give  the  pitch  desired,  and  the 
roof  framed  so  that  a  dormer-window  or  opening  is 
placed  upon  the  side  of  silo  from  which  it  will  be 
filled.  The  rafters  are  securely  fastened  to  the  wall 
by  bolts  imbedded  into  the  concrete  of  the  last 
course.  The  §  "  rods  used  as  vertical  reinforcement 
can  also  be  permitted  to  extend  above  the  last  course 
of  concrete  and  then  fitted  with  threads  and  a  nut  so 
as  to  bolt  the  rafter  at  the  foot,  cut  securely  to  the  wall 
of  silo.  The  space  between  rafters  is  now  filled  with 
concrete,  flush  to  the  top  edge  of  rafters,  and  over 
the  top  of  rafters  wire  lath,  or  expanded  metal  lath, 
is  nailed.  This  is  treated  to  a  plaster  coat  of  con- 


FIG.  16. — Details  of  constructing  concrete  silo  roof. 


62  PRACTICAL  SILO  CONSTRUCTION 

crete,  pressing  it  well  against  the  laih  to  press 
through  and  form  a  secure  key.  This  should  not  be 
less  than  l|"in  thickness,  and  is  best  at  about  2" or 
2J ".  The  rafters  must  be  spaced  close  enough  so 
that  the  metal  lath  will  not  sink  or  bend  under  the 
weight  of  the  concrete  placed,  or  they  may  be  rein- 
forced by  heavy  wires  stapled  to  the  rafters  every 
6"  apart  around  the  roof  for  the  first  3'  from  the 
eaves  upward. 

Before  the  plaster  coating  is  applied,  a  thin  wood 
strip  may  be  nailed  to  the  butt  ends  of  the  rafters  as 
a  fascia  or  finishing  strip  to  the  roof.  This  must  be 
thin,  so  as  to  bend  easily  to  the  circle.  In  placing  the 
concrete  plaster,  this  strip  will  be  of  value  in  getting 
the  eaves  or  edge  of  the  roof  even  and  symmetrical. 
The  concrete  for  the  roof  will  give  the  best  satis- 
faction when  made  in  the  proportions  of  1:3,  using 
sharp,  well-graded  sand. 

ORNAMENTAL   ROOF    OR   WALL   FOR   SILO 

At  Fig.  17  is  shown  an  ornamental  wall  for  the 
silo  that  extends  above  the  top  of  the  roof.  This  is 
in  the  form  of  a  parapet,  with  embrasures  and 
merlons  molded  to  suit  the  wishes  of  the  builder. 
The  diameter  of  the  parapet  is  4  inches  more  than 
the  diameter  of  the  silo.  This  requires  a  2 "  strip 
to  be  placed  at  the  bottom  of  mold  for  parapet,  as 
shown  in  illustration  (Fig.  18).  The  inside  mold  for 
this  part  of  the  wall  is  4  "  more  in  diameter  than  the 
silo,  thus  molding  a  2"  ledge  entirely  around  the 


FIG.  17. —Ornamental  roof  for  concrete  silo, 


FIG.  18. — Details  of  constructing  ornamental  roof  to  silo. 


PRACTICAL  SILO  CONSTRUCTION  65 

inside  of  the  silo  for  the  placing  of  rafters  for  the 
roof.  This  ledge  is  placed  so  that  it  will  be  even 
with  the  embrasures  entirely  around  the  parapet, 
thus  enabling  the  water  to  be  easily  carried  off  from 
the  roof. 

The  concrete  is  filled  into  mold  up  to  the  point 
where  the  ledge  is  placed,  then  the  wood  forms  for 
embrasures  are  set  inside  the  mold  at  the  desired 
distances  apart,  and  the  concrete  tamped  around 
same  to  the  top.  These  wood  forms  are  constructed 
of  three  short  boards,  with  the  center  one,  or  cross- 
piece,  bored  to  supply  a  hold  for  removing  the  form 
from  the  concrete.  The  construction  of  forms  is 
shown  at  Fig.  18,  with  the  method  of  placing  and 
filling  the  form  with  the  concrete. 


INDEX 

PAGE 

Adjusting  forms  for  various  sizes  of  silos 31 

Adjusting  forms  for  thickness  of  walls 32 

Advantages  of  the  concrete  silo  over  other  types 14 

Air-chamber  in  plaster  silo 41 

Amount  of  silage  fed  daily 17 

Assembling  silo  form 26-29 

Automatic  clamp  applied  to  silo  forms 35-37 

Bending  steel  centering 30 

Blocks  for  silo  construction 41-45 

Breaking  joints  in  laying  silo  blocks 47-49 

Brush  coat  of  neat  cement,  value  of 15 

Building  silo  forms 26-28 

Clamps  used  on  silo  forms 25-36 

Concrete  for  plastered  silos 50 

Concrete  for  silo  construction 49 

Construction  of  silo  block  molds 43-44 

Continuous  door  opening: 

block  silos 47-48 

monolithic  silos 59-60 

Cores  for  silo  block  molds 42-43 

Doors  for  silos : 

block  silos 46ni7 

construction 55-57 

continuous 57-60 

monolithic  silos 55-60 

plaster  silos 40 

reinforcing 57-58 

size  of 55 

Dry-firing,  cause  of 19 

67 


68  INDEX 

PAGE 

Ensilage  defined 14 

Fastening  sections  of  mold  together 31 

Floor  of  silo,  how  placed 19 

Footing  course,  size  of 20 

Foundation  of  silo : 

concrete  for  same 22 

with  floor  at  ground-level 20-21 

with  floor  below  ground-level 23-24 

Freezing  of  silage,  how  prevented 16 

Groove  molded  in  block  for  reinforcement 43 

History  of  the  silo 13 

Horizontal  reinforcement  or  "hoops" 53 

Laying  silo  blocks 45-46 

Location  of  silo 19 

Metal  centering  for  silo  construction 36-37 

Method  of  raising  forms 32-33 

Mold  for  silo  blocks 41-42 

Molding  ornamental  roof  to  silo 62-65 

Molding  silo  blocks 45 

Monolithic  silo  walls : 

with  continuous  air-chamber 37-41 

without  air-chamber 23 

Ornamental  roof  for  silos 62-65 

Plaster  silos,  how  built 38-39 

Proportions  of  the  silo 18 

Rafters,  how  fastened  to  the  silo  walls 60 

Reinforcement  of  silos 50-54 

Reinforcement  placed  in  silo  blocks 45 

Requisites  of  a  successful  silo 14-15 

Roof  for  silos : 

monolithic 60-61 

ornamental 62-63 

reinforcing. .  62 


INDEX  69 

PAGB 

Sheet  metal  used  as  centering 25-26 

Side  pressure  exerted  by  silage. 54 

Size  of  silo  to  erect 17-18 

Tables : 

capacity  of  silo  per  foot  of  height 18 

footing  courses  for  silos 20 

horizontal  reinforcement  of  silos 53 

steel  sheets  and  clamps  required 80 

vertical  reinforcement  for  silos 52 

Tackle  to  raise  forms 33-34 

Thickness  of  wall  in  plaster  silo 40 

Tying  reinforcement  with  wire 54 

Vertical  reinforcement 52 

Vertical  or  plumb  line,  how  assured 35 

Waterproofing  the  silo 15-16 

Weight  of  a  cubic  foot  of  silage 17 

Weight  of  steel  centering 28 

Wet  mixture,  advantages  of 50 

Wire  lath  used  in  plaster  silo 40 

Wood  clamp  for  silo  forms 25-27 


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